During the systematic studies of antitumor antibiotics, a novel antitumor antibiotic BMG 162-aF2, which was named spergualin, was found in a culture filtrate of a strain BMG 162-aF2 (FERM-P 5230; ATCC 31932) of Bacillus laterosporus belonging to the genus Bacillus [Takeuchi et al., Journal of Antibiotics, Vol. 34, p. 1619 and p. 1622 (1981), and Umezawa et al., U.S. patent application Ser. No. 297,458 filed Aug. 28, 1981 now U.S. Pat. No. 4,416,899]. The chemical structure of spergualin is represented by the formula ##STR7## The configuration at the position 15 is S, while that at the position 11 is yet to be determined [Journal of Antibiotics, Vol. 34, 1622 (1981)]. The compound of this formula is synthesized by the condensation of the acid amide and glyoxylylspermidine (Umezawa et al., U.S. patent application Ser. Nos. 375,916, now abandoned, and 375,950, now U.S. Pat. No. 4,430,346, filed May 5 and May 7, 1982, respectively). The resulting epimeric compound is resolved into natural (-)-spergualin and non-natural (+)-spergualin [Journal of Antibiotics, Vol. 34, 1625 (1981)].